Roasty McRoastface

The overly simple coffee roasting controller

https://github.com/sarumpaet/RoastyMcRoastface

So that popcorn maker that you MacGyvered to roast your coffee beans turns out to be a bit tedious to babysit while roasting. Also, you want some better control over its temperature curve. What you don't want is buying a huge proper roaster or assemble anything overly complex.

Time for Roasty McRoastface.

• Simple inexpensive ESP32-based design to control temperature curve.
• No PCB needed. No tinkering with 110/230V needed.
• Uses a roasting thermometer for temperature measurement.
• Controls fan/temperature using a servo connected to the fan power supply voltage adjustment control.
• ESP32 side firmware is minimal. Actual control is done in JavaScript on web client side. It's quite hackable.
• Adjustable temperature curve that gets stored in your browser.
• Initial Wifi configuration done via access point mode wifi.
• Failsafe: If connection to the JavaScript control client is lost, the fan gets turned up.
• Heating can get turned off at cycle end using a wifi-enabled power outlet (e.g., Tasmota).
• Future: Temperature probe sanity checks and failsafe.

Some things Roasty cannot do:

• For simplicity's sake there's no own display. Everything is controlled via the web client.
• The web client is needed during operation. Make sure your wifi is stable and your phone or notebook doesn't go to sleep while roasting.

THIS IS WORK IN PROGRESS AND NOT END USER READY IN ANY WAY.

Beware! Stuff is running at high temperatures that represent a fire hazard. Bean chaff is flammable. Do not run unsupervised. Use at your own risk.

The web UI.

Hardware

Roasting thermometer probe, controller, fan power source.

• ESP32 Dev Kit v1
• 100nF capacitor parallel to (NTC) temperature probe
• Probe between 3.3V and D35/GPIX35
• Resistor between GND and D35/GPIX35 (value depends on probe, 3.8k worked fine for me, make sure max current is about 1mA)
• Servo connected to VIN, GND, GPIO13 (Vcc and GND wires have been switched compared to normal servo pinout in pic)

Hot glue to the rescue.

• Make sure the servo range physically doesn't allow running the fan very low or even turning it off. Fire hazard!

Modded PC3751 popcorn machine.

• Note the fan has been disconnected from the 230V supply by cutting PCB traces.
• Make sure the fan wires are fastened in place securely. Best glue them additionally.